1. Field of the Invention
The invention relates to an exhaust gas purification catalyst with excellent oxidation activity, and particularly on exhaust gases that include carbon monoxide (CO) or hydrocarbons (HC), and to a method for manufacturing this catalyst.
2. Description of the Related Art
Exhaust gas from internal combustion engines used in vehicles and so forth contains CO, unburned HC, and other such components that are harmful to humans. Accordingly, the exhaust system of a typical vehicle is provided with an exhaust gas purification device that decomposes and removes harmful components. This device is equipped with an exhaust gas purification catalyst whose-main component is a platinum group element such as platinum, rhodium or palladium (Pd) supported on a metal oxide such as alumina. Of these platinum group elements, Pd conventionally has superior performance in the oxidative removal of CO, unburned HC, and the like, and is widely used not only as part of a three-way catalyst for gasoline engines, but also as an oxidation catalyst for diesel engines, and a catalyst for lean-burn engines.
Technology related to metal supported catalysts that are supported on a carrier and contain Pd has been developed. Japanese Patent Application Publication No. 2009-011951 (JP-A-2009-011951) discloses technology for an alloy cluster catalyst in which a Pd-gold (Au) alloy cluster having a composition in which the Pd:Au atomic ratio is 3:1 is supported as a catalyst active species on the surface of a carrier composed of a metal oxide.
JP-A-2009-011951 discloses in working examples the results for simulation of the adsorption energy on a titanium dioxide (TiO2) carrier of a Pd—Au alloy, but there is substantially no disclosure at all of the exhaust gas purification effect, and therefore the degree to which the alloy cluster catalyst disclosed in JP-A-2009-011951 exhibits activity is not considered at all.